MUNSON: SPERMATOGENESIS OF PAPILIO. 
59 
cylindrical with one end rounded, the other pointed (pi. 12, fig. 15-23; 
pi. 14, fig. 40-43). 
The cyst cell at the rounded end of the cyst finally develops into a 
very large cell, the head nurse-cell (pi. 14, figs. 43, 44, 48, 54). With 
this head nurse-cell the heads of the developing spermatozoa finally 
become connected (pi. 14, fig. 43). At first it is a very much flattened 
cell, in no way differing from the other cyst cells, but as the sperma¬ 
tids develop, they seem to shift their position, so that all have their 
nuclear end turned toward or connected with one cyst cell only. 
This then increases in thickness (pi. 14, fig. 50), occasionally appear¬ 
ing oval as in plate 14, figure 49. (Compare also pi. 14, figs. 49, 50, 
54, h. n.) While this head nurse-cell curves slightly to include the 
heads of the growing spermatozoa (pi. 14, figs. 48, 50, 54), the other 
cyst cells grow into the form of a hollow cylinder enclosing the bundle 
of spermatozoa. Plate 14, figure 52, shows one of these in section 
transverse to the long axis of the spermatocyst. (Compare with this 
also pi. 14, fig. 43, c. c.) From the anterior head nurse-cell, the cyst 
cells diminish in thickness backward, till they become so thin as to 
be scarcely visible. I have occasionally found one of these cells at 
the tail end of the cyst in the early stage of development, but that is 
an exception rather than the rule. 
The head nurse-cell varies considerably in shape during the devel¬ 
opment of the spermatocyst; but it ultimately becomes the largest 
cell and more or less spherical in shape. It has a large oval or irregular, 
rarely spherical nucleus (pi. 14, figs. 43, 44, 48, 54, h. n.). The nucleus 
is rich in chromatin arranged in the form of a network, which is some¬ 
times massed irregularly (pi. 14, fig. 54). There is usually a conden¬ 
sation of the chromatin at one point, which can hardly be called a 
true nucleolus, though it is the only body present to suggest one. 
The cytoplasm is greatly developed. In the living cyst it is bright 
and nearly transparent (pi. 17, fig. 151). In preserved material, it 
shows a distinct and well developed cytoreticulum. The other cyst 
cells agree in these respects (pi. 14, fig. 54, c. c., h. n.). 
Abnormal Spermatocysts. 
Very rarely spermatocysts are found having the appearance repre¬ 
sented in plate 14, figure 45. It consists of a spherical mass of nuclei 
with little or no cytoplasm surrounding each, and with little or no 
